ASPIRATION OF OOCYTES FOR IN-VITRO FERTILIZATION

An aspiration system, incorporating a regulated vacuum pump, was used to examine, in vitro, some factors that may affect oocyte collection, In an open aspiration system, as the length of the needle was increase d, or the internal diameter decreased, the velocity (and flow rate) of aspirated fluid decreased, There was a difference, however, between e xperimental flows and those predicted by Hagen-Poiseuille's Law, Upon application of vacuum to a closed aspiration system, employing isolate d bovine ovaries, there was an initial rapid increase in the collectio n tube vacuum to 85% of the selected pump vacuum followed by a more gr adual rise to 100%, The vacuum within the needle similarly rose rapidl y to approximately half the selected vacuum, while the vacuum at the n eedle tip was similar to 5% of selected vacuum, The vacuums throughout the system briefly equilibrated as maximum flow/velocity was reached. Flow/velocity slowed dramatically as the follicle collapsed, and stop ped as the needle tip was blocked, If vacuum was maintained during the withdrawal of the needle from the follicle, there was a dramatic forw ard flow of fluid toward the collection tube, The morphological appear ance of bovine cumulus after in-vitro aspiration was generally unalter ed by vacuums commonly utilized in oocyte collection, providing the cu mulus was regular, compact and refractile. The cumulus was less resist ant to aspiration if it was damaged or had degenerated. These results suggest that an intact cumulus may offer protection during oocyte coll ection.